I just came back from a two week trip in Italy. When we rented the car, I presented both my UK and US driving licences.
The man working had to think a bit but he asked where I currently lived. When I said I lived in the UK, he said he'd use the US license for the rental. If I got any ticket in Italy it would go on that rather than points on my UK licence!

Just a thought for anyone else renting a car with both UK and US licences.
